In railcars, power supply from a carbody to a motor and power collection from a third rail (power supply rail) to the carbody by a current collector provided at a bogie are performed through electric cables. Since the carbody and the bogie are separated from each other at the time of maintenance, the electric cable is configured to be disconnectable at a connector or an electrical junction box. The connector or the electrical junction box is attached to a bogie frame of the bogie, and all of these components are exposed to an outer space.
Therefore, if the electrical junction box is exposed to rain water or car washing water at the time of car washing (hereinafter simply referred to as “water”), the water may intrude into an inside of the electrical junction box. For example, to prevent the water from intruding through a cable introducing portion into which the electric cable is inserted, known as a waterproofing measure of the electrical junction box is a configuration including: an elastic member having a through hole through which the electric cable penetrates; and divided press casings covering the elastic member (see Japanese Laid-Open Patent Application Publication No. 2011-171617, for example).
Known as one example of the electrical junction box is an electrical junction box including: a box main body which is open upward; and a cover covering the box main body from above. According to this electrical junction box, if the waterproofing between the box main body and the cover is incomplete, the water easily intrudes into the inside of the electrical junction box from outside. One example of a waterproofing structure is a structure in which a gasket made of rubber is provided in a groove formed at a coupling portion between the box main body and the cover. However, if the gasket is fitted in the groove which includes not only straight portions but also curved and/or meandering portions, a contact state between the box main body and the cover may become unstable, and the water may intrude into the inside of the electrical junction box.
If the gasket is attached to the cover, the gasket may fall off from the cover when attaching the cover to the box main body.
To prevent the contact state of the gasket from becoming unstable and also prevent the gasket from falling off, the gasket needs to be provided in the groove without any gap. However, the electrical junction box is exposed to the outer space, so that there is a possibility that when the electrical junction box is placed under a high-temperature circumstance during the operation of the railcar or the like, the gasket made of rubber expands by heat, and pressure generated by the heat expansion of the gasket is applied to the box main body or the cover, and as a result, the box main body or the cover deforms.
An object of the present disclosure is to provide a gasket for an electrical junction box of a railcar, the gasket being capable of securing water-tightness between a box main body and a cover, preventing the gasket from falling off when attaching the cover, and reducing pressure applied to the box main body or the cover by the heat expansion of the gasket, and the electrical junction box of the railcar.